android自定义adapter之简单写法

    自定义adapter比较常用，很多人还在使用extends BaseAdapter，然后写一大堆重复的代码，这里是提供一个封装的工具类，把重复的代码都省略掉，让adapter变的简洁一些。

    给控件设置adapter的调用代码大概是这样

mGridView.setAdapter(new CommonAdapter<GridBean>(mContext, list, R.layout.item_main_shouye_grid) {
            @Override
            public void convert(ViewHolder helper, GridBean item) {
                helper.setText(R.id.tv_item, item.name);
                helper.setImageResource(R.id.iv_item, item.icon);
                ImageView imageView = helper.getView(R.id.image);
                //DO your buisness with imageview
            }
        });

指明该adapter填充的数据类型，context，数据集data，和单项的布局文件，然后就是给各控件set值了。这样写adapter就比较简洁了。

CommonAdapter代码

package com.ab.hongyang;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import java.util.List;

/**
 * Created by wuwf on 2015-04-07.
 */
public abstract class CommonAdapter<T> extends BaseAdapter {
    protected LayoutInflater mInflater;
    protected Context mContext;
    protected List<T> mDatas;
    protected final int mItemLayoutId;

    public CommonAdapter(Context context, List<T> mDatas, int itemLayoutId) {
        mInflater = LayoutInflater.from(context);
        this.mContext = context;
        this.mDatas = mDatas;
        this.mItemLayoutId = itemLayoutId;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHolder viewHolder = getViewHolder(position, convertView,
                parent);
        convert(viewHolder, getItem(position));
        return viewHolder.getConvertView();
    }

    public abstract void convert(ViewHolder helper, T item);

    private ViewHolder getViewHolder(int position, View convertView,
                                     ViewGroup parent) {
        return ViewHolder.get(mContext, convertView, parent, mItemLayoutId,
                position);
    }

    @Override
    public int getCount() {
        return mDatas.size();
    }

    @Override
    public T getItem(int position) {
        return mDatas.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }
}

ViewHolder.java

package com.ab.hongyang;

import android.content.Context;
import android.graphics.Bitmap;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.ab.R;
import com.ab.hongyang.imageloader.ImageLoader;

public class ViewHolder {
    private final SparseArray<View> mViews;
    private int mPosition;
    private View mConvertView;
    private Context mContext;

    private ViewHolder(Context context, ViewGroup parent, int layoutId,
                       int position) {
        mContext = context;
        this.mPosition = position;
        this.mViews = new SparseArray<View>();
        mConvertView = LayoutInflater.from(context).inflate(layoutId, parent,
                false);
        //setTag
        mConvertView.setTag(this);
    }

    /**
     * 拿到一个ViewHolder对象
     *
     * @param context
     * @param convertView
     * @param parent
     * @param layoutId
     * @param position
     * @return
     */
    public static ViewHolder get(Context context, View convertView,
                                 ViewGroup parent, int layoutId, int position) {

        if (convertView == null) {
            return new ViewHolder(context, parent, layoutId, position);
        }
        return (ViewHolder) convertView.getTag();
    }


    /**
     * 通过控件的Id获取对于的控件，如果没有则加入views
     *
     * @param viewId
     * @return
     */
    public <T extends View> T getView(int viewId) {

        View view = mViews.get(viewId);
        if (view == null) {
            view = mConvertView.findViewById(viewId);
            mViews.put(viewId, view);
        }
        return (T) view;
    }

    public View getConvertView() {
        return mConvertView;
    }

    /**
     * 为TextView设置字符串
     *
     * @param viewId
     * @param text
     * @return
     */
    public ViewHolder setText(int viewId, String text) {
        TextView view = getView(viewId);
        view.setText(text);
        return this;
    }

    /**
     * 为ImageView设置图片
     *
     * @param viewId
     * @param drawableId
     * @return
     */
    public ViewHolder setImageResource(int viewId, int drawableId) {
        ImageView view = getView(viewId);
        view.setImageResource(drawableId);

        return this;
    }

    /**
     * 为ImageView设置图片
     *
     * @param viewId
     * @return
     */
    public ViewHolder setImageBitmap(int viewId, Bitmap bm) {
        ImageView view = getView(viewId);
        view.setImageBitmap(bm);
        return this;
    }

    /**
     * 为ImageView设置图片
     *
     * @param viewId
     * @param url
     * @param url    是否是网络图片
     * @return
     */
    public ViewHolder setImageByUrl(int viewId, String url, boolean isNet) {
//        AbImageLoader.getInstance(mContext).display((ImageView) getView(viewId), url);
        ImageView imageview = getView(viewId);
        imageview.setImageResource(R.drawable.pictures_no);
        ImageLoader.getInstance(3, ImageLoader.Type.LIFO).loadImage(url, imageview
                , isNet);
        return this;
    }


    public int getPosition() {
        return mPosition;
    }
}

这个类提供了一些给textview和imageview填充值的方法，setImageByUrl是展示网络图片的，这个方法里替换为你自己的加载图片框架即可。推荐使用glide。

    相信CommonAdapter会给自定义adapter带来极大的方便